Murphy, Stuart J.,  1942- <br/><br/>
Dave's down-to-earth rock shop / 
by Stuart Murphy ; illustrated by Cat Bowman Smith. 
 - New York, NY :  HarperCollins,  c2000. 
 - 33 p. :  col. ill. ;  22 x 26 cm. 
 - MathStart. .
<br/><br/> "Classifying; Level 3." 
<br/><br/> As they consider sorting their rock collection by color, size, type, and hardness, Josh and Amy learn that the same objects can be organized in many different ways. 
<br/><br/><label>LCCN: </label>98-032128 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Set theory--Juvenile literature.
<br/><br/><label>LC Class. No.: </label>QA248  / .M78 2000